The molecular epidemiology of human and animal rotaviruses is being studied by hybridization and sequencing techniques with four major objectives: (1) investigate the role of outer capsid protein VP4 in the virulence of human rotaviruses; (2) develop hybridization probes specific for the genes of VP4 and VP7 (the two outer capsid proteins) for identification of rotavirus serotypes and delineation of their relative distribution; (3) identify and characterize new VP4 and VP7 serotypes in human and animal rotavirus strains; and (4) determine the relative proportion of the neutralizing antibody response to natural rotavirus infection that is specific for each of the outer capsid proteins, VP4 and VP7.